What is Trophic Cascade?


Otero, P., & Mar, M.D. (2017). Controlling mesopredators: importance of behavioural interactions in trophic cascades.

What is Trophic Cascade?

Trophic cascade is an ecological phenomenon triggered by the removal or addition of top predators and involving changes in the relative population of predator and prey through a food chain. In 1995, wolves were introduced in the Yellowstone National Park by the United States. The wolves gave life to many other species in the park. Before the wolves were introduced, herbivores such as deers managed to reduce the amount of vegetation. After the introduction of the wolves, deers were being killed by the wolves and the valleys and gorges regenerate. In just six years, trees started to grow taller, and more vegetation were observed. The number of birds and beavers started to increase. Beavers started to build dams which are important for the habitat of fish, reptiles, and amphibians. The number of rabbits and mice also increased because the wolves started killing the coyotes. In addition, the number of eagles, weasels, and foxes also increased. The bears also increased in numbers because they started to feed on the carrion that the wolves have left. Berries started to regenerate and the reason why the population of the bears grew. The introduction of the wolves also changed the behavior of the rivers. As vegetation increases, the erosion decreases. The channels narrowed and there were more water pools which are all great for wildlife habitat. The regenerated forest stabilized the banks and the river started to flow in a straight path. The wolves transformed the ecosystem of the Yellowstone National Park and the physical geography.

Trophic cascade is an ecological phenomenon triggered by the removal or addition of top predators and involving changes in the relative population of predator and prey through a food chain. Whales eat fish and krill, but studies show that as whale declines, so as with the fish and krill. Researchers found out that whales not only eat fish, but they also keep them alive. The whales help maintain the living system of the ocean. Whales normally feed on the dark depths of the ocean, but they rise to the surface where photosynthesis occur. At the ocean surface, whale releases fecal plumes which are rich in iron and nitrogen. Iron and nitrogen are usually scarce at the ocean surface. These nutrients help fertilize plant plankton that lives where the plant can survive which is the photic zone. Whales also keep the plankton at the surface of the ocean by kicking them back when the plankton sinks. When there are more plant plankton, it means there are also more animal plankton which the larger animal feeds. When there are more whales, there will be more fishes and krill. Plankton not only feeds the creatures of the sea but also absorbs carbon dioxide from the atmosphere. Eventually, plankton sinks to the ocean floor bringing the carbon dioxide it absorbed and remains there for thousands of years. If there are more whales, there will be more plankton, and if there are more plankton, there will be less carbon dioxide in the air. Carbon dioxide was confirmed to be one of the causes of global warming. In summary, whales can change the climate.

The Tasmanian devil of Australia help maintain the entire forest ecosystem. During the British arrival in Australia, foxes and cats was introduced and ate much vegetation in their way out across the continent. The less vegetation led to the decrease in population of smaller animals which are essential for maintaining the health of ecosystem. Most of these smaller animals dig to the ground and help mix the organic matter into the soil. Burying of dead leaf reduces fuel loads creating condition for cooler and less destructive bush fires. The introduction of Tasmanian devils led to population decrease of cats which results in the increase of population in smaller animals. The Tasmanian devils allow the smaller native animals to perform their role as ecosystem engineers.

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